NAD vs. Adcom

No doubt, some speakers are inefficent and thus require some 'ooomph' to make them sing. However, you may find that a good separate pre-amp may make more of an improvement dollar for dollar than upgrading your amp, especially since you are bi-amping.

Interesting that no one has commented about your bi-amping with different amps. I've always heard that it is recommened to use identical amps when bi-amping. I wonder if using identical amps would improve the 'singing' ability of your speakers?

Don't over look B&K amps. I recently heard one and was impressed given money spent.

No comments on the possibility of the NAD Silverline S200 amp [probably in conjunction with the S100 preamp]?

I'd guess the bi-amping with such dissimilar amps may be the 'problem'.

Almost any single more powerful amp will help. A good integrated which can handle the B&W load, not just impedance but phase angle as well, is recommended.

Maybe a NAD in the 37x series? That is, if you like the NAD house sound?

One of the M series integrates would work like mad, but the cost may be a little brisk.

BiPolar? MOSFET? Good bad exist with either device type. If it works well with your speakers, don't let either deter you.